Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires wp-cli/wp-cli-tests ^5 -> satisfiable by wp-cli/wp-cli-tests[v5.0.0, v5.0.1, v5.0.2]. - wp-cli/wp-cli-tests[v5.0.0, ..., v5.0.2] require wp-cli/core-command ^1 || ^2 -> satisfiable by wp-cli/core-command[dev-main, v1.0.0, ..., v1.0.12, v2.0.0, ..., 2.x-dev (alias of dev-main)] from composer repo (https://repo.packagist.org) but wp-cli/core-command dev-copilot/add-delete-old-core-files is the root package and cannot be modified. See https://getcomposer.org/dep-on-root for details and assistance.